Otis hutchins



O. HUTCHIYNS.

ELECTRIC FURNACE.

APPLICATION FILED NOV-18, 191s.

Patent-ed July 15, 1919.

INVENTOR WITNESSES 2M M i UNITED STATES PATENT OFFICE.

OTIS HUTCHINS, OF NIAGARA FALLS, NEW YORK, ASSIGNOR TO THE CARIBORUNDUM COMPANY, OF NIAGARA FALLS, NEW YORK, A CORPORATION OF PENNSYLVANIA.

ELECTRIC FURNACE.

Specification of Letters Patent.

Patented July 15, 1919.

Application filed November 18, 1918. Serial No. 262,949.

To all whom it may concern:

Be it known that I, OTIS HUTCHINS, a citizen of the United States, residing at Niagara Falls, in the county of Niagara and State of New York, have invented a new and useful Improvement in Electric Furnaces, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, forming part of this specification, in which Figure 1 is a vertical section of an electric furnace embodying my invention.

Fig. 2 is a section of a portion of a fur-' manufacture of aluminous abrasives consist of an iron base, usually mounted u on wheels, the base containing a bed of car on a foot or more in thickness. The side walls of the furnace or crucible are made removable from the base so that they may be taken away and leave the finished ingot supported entirely on the base. One type of furnace in use consists of a conical iron shell which has a smaller area at its top than at its bottom so that it can be lifted from the'solidified ingot and which fits down over the carbon bed and is supported by the base. This iron shell is either water or air cooled. Another type of furnace consists of a base, such as described above, upon which four brick walls are mounted and locked together, thus forming the crucible. In this furnace the sides are vertical and the bottom of the furnace has the same area as the top.

In the operation of these existing furnaces, the shell is either placed upon or assembled upon the base and secured in place. The aluminous charge is introduced and is melted by means of an electric current. As the charge melts down, fresh ore is added until the crucible is full of molten abrasive. This is now allowed to cool and solidify, after which the sides of the crucible are removed by lifting the iron shell in the one case, or by taking off the brick sides in the other case. The ingot or pig of abrasive is now rolled or lifted off the base by a crane and is removed to a-suitable place for further cooling. The shell or sides of the crucible are then remounted upon the base and the furnace is ready for another run.

A serious objection connected with the manufacture of aluminous abrasives in furnaces of the types above described, is due to the contamination of the melt by the carbon bottom of the crucible. It is well known to those skilled in this art that it is exceedingly important to maintain the proportions of the aluminous charge within very narrow limits; and that avariation of as much as one per cent. in the carbon content of the mixture will cause a marked difference in the quality of the aluminous material produced. lVhen an aluminous charge is melted in contact with a carbon hearth, a variable amount of carbon is absorbed into the mixture thus causing a serious variation in the quality of the product produced, the lower portions of the pig of abrasive being always subjected to greater reduction than the upper portions. The amount of this contamination depends upon the exposed area of the carbon hearth as compared with the total volume of the furnace. I

Myv invention is designed to reduce thls contamination to a negligible amount; and

' to also provide a furnace from which the pig or ingot of an abrasive can be removed with great ease and entirely eliminating the time and labor required to remove the sides of the crucible after each run.

I accomplish the first of these objects by making a crucible whose carbon hearth is of a smaller area thanthe cross sectional area of the top of the crucible. I have found that it is possible to use a hearth in a furnace of this type which hasless than onefourth the area required in a furnace of equal capacity having a crucible which is larger at the bottom that it is at the top. If desired, it is possible to water cool the shell of such a furnace successfully, as I have found the water will run down and adhere to the under side of an inclined surface even when the surface is inclined at an angle of more than 70 from the vertical.

In order to facilitate emptying the furnace, I provide a construction in which the sides andbase are permanently united in a unitary structure; so that when a run has been finished and an abrasive solidified, the

and larger at the top than at the bottom.

It is provided with side projections 3 of trunnion form by means of which the pot can be lifted by a crane and turned bottom side up. 4 designates the carbon hearth of thefurnace. 5' is a water pipe which surrounds the upper portion 'of the crucible and which has numerous small holes through which water may be discharged downwardly against the sloping outer surface of the crucible to effectually cool it.

The furnace illustrated in this figure is the simplest form of my invention. I do not, however, wish to limit myself to this form as the structure may be varied in many respects. I may, for instance, use an air cooled iron shell such as shown at 6 in Fig. 3, whose outer surface is su plied with a plurality ofheat radiating ns or projections 7. I may also use a furnace having a brick lining such as indicated at8 in Fig. 2. The furnace may be placed either upon a stationary or'movable substructure, asmay be desired, and various changes can be made in the details of construction thereof without departing from the spirit and scope of the appended claims.

I claim: 1. An electric pot furnace having a unitary base and sides and havingfa hearth which is smaller in area than the top opening of the furnace, with means whereby wasurface of the furnace; substantially as described.

3. An electrical pot furnace, comprising an invertible pot or crucible, having a carbon hearth which is smaller in area than the top opening of the furnace and which is provided with radial projections whereby it may be lifted and inverted, and means for applying cooling fluid to the exterior surface of the crucible, substantially as described.

In testimony whereof, I have hereunto set my hand.

OTIS HUTCHINS. 

